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Abstract

The reverse bending and straightening test is conducted on wires used for civil engineering applications to detect laminations which can pose a threat to the integrity of the wires. The FE simulations of the reverse bending and straightening of wires with laminations revealed that the reverse bending and straightening test is only effective in revealing or detecting near-surface laminations with lengths from 25 mm located up to 30% of the wire’s thickness and may not be an effective test to detect mid-thickness, near-mid-thickness, and short near-surface laminations with lengths below 15 mm. This is because wires with mid-thickness, near-mid-thickness and short near-surface laminations will pass through the reverse bending and straightening procedures without fracturing and therefore mid-thickness, near-mid-thickness and short near-surface laminations may go undetected. Consequently, other in-line non destructive testing methods might have to be used to detect mid-thickness, near-mid-thickness and short near-surface laminations in the wires.
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Abstract

Author presents an analytical method of calculation of unit power losses in magnetic laminations used in electrical machines and transformers. The idea of this method, based on the solution of Maxwell's equations in the lamination material, was described by the author in the previous work [3], taking into account approximation of constitutive static hysteresis loop by elliptic form of the function B = f(H) depending on magnetic saturation. In the previous formula for new isotropic and anisotropic materials it is needed to introduce so called "anomaly coefficient" deduced from the comparison of measured and calculated value of power losses in arbitrary excitation frequency for assumed induction. The method was tested by comparison with the results of experiments presented in commercial catalogues [1, 2]. Assuming superposition of harmonic power losses it is possible to enlarge this method for the estimation of overloss coefficient in dynamo sheet during axial magnetization with nonsinusoidal flux generated e.g. by PWM voltage supply.
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